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United States Patent |
5,151,842
|
DeBiasi
,   et al.
|
September 29, 1992
|
Switchboards and panelboards having interlock and load selection
capabilities
Abstract
Switchboard and panelboard enclosures include a main electronic circuit
breaker interconnected with a plurality of branch circuit breakers by
means of a corresponding plurality of terminal boards.
Zone-Selective-Interlock and Load Selection functions are achieved by
signals transmitted between the branch circuit breakers and the main
circuit breaker. The accessories within the branch circuit breakers
respond to tripping signals from the main circuit breaker to provide the
Zone-Selective-Interlock and Load Selection functions.
Inventors:
|
DeBiasi; Mark S. (Windsor, CT);
Menelly; Richard A. (Burlington, CT)
|
Assignee:
|
General Electric Company (New York, NY)
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Appl. No.:
|
687649 |
Filed:
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April 19, 1991 |
Current U.S. Class: |
361/93.2; 361/634 |
Intern'l Class: |
H02H 003/00; H02B 001/04 |
Field of Search: |
361/93,94,95,96,115,353
|
References Cited
U.S. Patent Documents
4468714 | Aug., 1984 | Russell | 361/62.
|
4476511 | Oct., 1984 | Saletta et al. | 361/96.
|
4589052 | May., 1986 | Dougherty | 361/94.
|
4672501 | Jun., 1987 | Bilac et al. | 361/96.
|
4754247 | Jun., 1988 | Raymont et al. | 335/202.
|
4794273 | Dec., 1988 | McCullough et al. | 307/139.
|
4858056 | Aug., 1989 | Russell | 361/93.
|
4860157 | Aug., 1989 | Russell | 361/156.
|
4894631 | Jan., 1990 | Castonquav et al. | 335/167.
|
4991042 | Feb., 1991 | Tokarski et al. | 361/93.
|
5051861 | Sep., 1991 | Purkayastha et al. | 361/96.
|
Other References
Ser. No. 674.475 entitled An Electronic Circuit Interrupter with Attached
Terminal Connector Block", Filed Mar. 25, 1991, Lesslie et al. (Docket
41PR-6894).
|
Primary Examiner: Stephan; Steven L.
Assistant Examiner: To; E.
Attorney, Agent or Firm: Menelly; Richard A.
Claims
Having thus described our invention, what we claim as new and desire to
secure by Letters Patent is:
1. A circuit breaker interconnect arrangement comprising in combination:
a main circuit breaker having a main electronic trip unit including a
microprocessor, said main circuit breaker arranged for interrupting
current through a protected main circuit;
a main terminal board connecting with said microprocessor and with a
plurality of main terminals arranged on said main terminal board;
a first branch circuit breaker having an associated first electronic trip
unit and a first actuator unit, said first trip unit having first
indicating means outputting a first pick-up signal indicating the
occurrence of an overcurrent condition through an associated first branch
circuit, said first actuator unit having means for interrupting current
through said first branch circuit; and
a first branch terminal board connecting with said first electronic trip
unit, said first actuator unit and said main terminal board whereby said
microprocessor inputs a first trip signal to said first actuator unit to
interrupt current through said first branch circuit upon receipt of said
first pick-up signal, wherein said first pick-up signal is received by
said microprocessor when said main trip unit is in pick-up whereby said
main trip unit is deterred from interrupting said main circuit until said
first trip signal interrupts said first branch circuit.
2. A circuit breaker interconnect arrangement comprising in combination:
a main circuit breaker having a main electronic trip unit including a
microprocessor, said main circuit breaker arranged for interrupting
current through a protected main circuit;
a main terminal board connecting with said microprocessor and with a
plurality of main terminals arranged on said main terminal board;
a first branch circuit breaker having an associated first electronic trip
unit and a first actuator unit, said first trip unit having first
indicating means outputting a first pick-up signal indicating the
occurrence of an overcurrent condition through an associated first branch
circuit, said first actuator unit having means for interrupting current
through said first branch circuit; and
a first branch terminal board connecting with said first electronic trip
unit, said first actuator unit and said main terminal board whereby said
microprocessor inputs a first trip signal to said first actuator unit to
interrupt current through said first branch circuit upon receipt of said
first pick-up signal, wherein said first pick-up signal is received by
said microprocessor when said main trip unit is not in pick-up whereby
said first trip unit interrupts said first branch circuit before said
microprocessor inputs said first trip signal.
3. A circuit breaker interconnect arrangement comprising in combination:
a main circuit breaker having a main electronic trip unit including a
microprocessor said main circuit breaker arranged for interrupting current
through a protected main circuit;
a main terminal board connecting with said microprocessor and with a
plurality of main terminals arranged on said main terminal board;
a first branch circuit breaker having an associated first electronic trip
unit and a first actuator unit, said first trip unit having first
indicating means outputting a first pick-up signal indicating the
occurrence of an overcurrent condition through an associated first branch
circuit, said first actuator unit having means for interrupting current
through said first branch circuit;
a first branch terminal board connecting with said first electronic trip
unit, said first actuator unit and said main terminal board whereby said
microprocessor inputs a first trip signal to said first actuator unit to
interrupt current through said first branch circuit upon receipt of said
first pick-up signal;
a second branch circuit breaker having an associated second electronic trip
unit and a second actuator unit, said second trip unit having means
outputting a second pick-up signal indicating the occurrence of an
overcurrent condition through an associated second branch circuit, said
second actuator unit having second indicating means interrupting current
through said second branch circuit; and
a second branch terminal board connecting with said second electronic trip
unit, said second actuator unit and said main terminal board whereby said
microprocessor inputs a second trip signal to said second actuator unit to
interrupt current through said second branch circuit upon receipt of said
second pick-up signal, wherein said first and second branch circuit
breakers are assigned first and second priorities whereby when said main
trip unit is in pick-up and neither said first nor second trip units are
in pick-up, said main trip unit thereby transmits a trip signal to said
second trip unit to interrupt said second branch circuit.
4. A circuit breaker interconnect arrangement comprising in combination:
a main circuit breaker having a main electronic trip unit including a
microprocessor said main circuit breaker arranged for interrupting current
through a protected main circuit;
a main terminal board connecting with said microprocessor and with a
plurality of main terminals arranged on said main terminal board;
a first branch circuit breaker having an associated first electronic trip
unit and a first actuator unit, said first trip unit having means
outputting a first pick-up signal upon occurrence of an overcurrent
condition through an associated first branch circuit, electrically in
series with said main circuit said first actuator unit having means for
interrupting current through said first branch circuit;
a first branch terminal board connecting with said first electronic trip
unit, said first actuator unit and said main terminal board;
a second branch circuit breaker having an associated second electronic trip
unit and a second actuator unit, said second branch circuit breaker being
electrically in series with said main circuit breaker and said first
branch circuit breaker, said second trip unit having means outputting a
second pick-up signal upon the occurrences of an overcurrent condition
through an associated second branch circuit, said second actuator unit
having means for interrupting current through said second branch circuit;
a second branch terminal board connecting with said second electronic trip
unit, said second actuator unit and said main terminal board;
a third branch circuit breaker having an associated third electronic trip
unit and a third actuator unit, said third branch circuit breaker being
electrically in parallel with said second branch circuit breaker, said
third branch circuit breaker having means outputting a third pick-up
signal upon occurrence of an overcurrent condition through a third branch
circuit, said third actuator unit having means for interrupting current
through said third branch circuit; and
a third branch terminal board connecting with said third electronic trip
unit, said third actuator unit and said main terminal board whereby said
microprocessor inputs a trip signal to said second actuator unit to
interrupt said second associated branch circuit upon receipt of said first
pick-up signal.
5. The circuit breaker interconnect arrangement of claim 4 wherein said
third associated branch circuit is electrically connected with prioritized
electrical equipment.
Description
BACKGROUND OF THE INVENTION
U.S. patent application Ser. No. 674,475 entitled "An Electronic Circuit
Interrupter with Attached Terminal Connector Board" describes a main
circuit breaker connected within a switchboard enclosure containing a
plurality of branch circuit breakers. The main and branch circuit breakers
each include individual terminal blocks that are arranged within the
switchboard enclosure. The main and branch circuit breakers communicate
with a central programming unit over a power-line communication network to
provide supplemental protection features.
The branch circuit breakers described within the aforementioned U.S. Patent
Application are so-called "smart" circuit breakers wherein each circuit
breaker contains its own microprocessor and software support programs. The
terminal boards connected with the individual circuit breakers provide the
means for connecting with the power-line communication link that connects
the central programming unit with the main and branch circuit breakers.
With Zone-Selective-Interlock function, wherein an upstream circuit breaker
is restrained from responding to interrupt a protective circuit until a
downstream circuit breaker closer to the source of the fault has
responded, there must be some means for communicating between the upstream
and downstream circuit breakers.
U.S. Pat. No. 4,468,714 entitled "Zone Selective Interlock Module for Use
with Static Trip Circuit Breakers" describes one such
Zone-Selective-Interlock system using hard-wired connections between the
upstream and downstream circuit breakers.
"Load Selection" as described herein concerns prioritizing the electrical
equipment loads that are connected with distributed branch circuit
breakers whereby selected circuit breakers are actuated to interrupt
operating power to non-essential equipment while the operating power to
those circuit breakers connected with essential equipment such as
computers, emergency lighting and medical apparatus is maintained.
U.S. Pat. No. 4,672,501 entitled "Circuit Breaker and Protective Relay
Unit" describes a "smart" circuit breaker which includes a microprocessor
programmed to perform the Load Selection function.
U.S. Pat. No. 4,589,052 entitled "Digital I.sup.2 T Pickup, Time Bands and
Timing Control Circuits for Static Trip Circuit Breakers" describes an
electronic trip unit useful for overcurrent protection, which does not
include a microprocessor. When such electronic trip units are used as
branch circuit breakers it would be highly advantageous to provide such
circuit breakers with Zone-Selective-Interlock and Load Selection
Functions.
U.S. Pat. No. 4,991,042 entitled "Digital Circuit Interrupter with Keypad
Data Entry and Display" describes a smart circuit breaker containing its
own microprocessor and associated circuitry for entering trip parameters
to the electronic trip unit and displaying the trip parameters along with
voltage and ampere ratings, upon command.
Accordingly, one purpose of the invention is to use a smart circuit breaker
as the main circuit breaker within a switchboard or panelboard enclosure
along with a plurality of distributed branch circuit breakers containing
electronic trip units such as described in the aforementioned U.S. Pat.
No. 4,589,052.
SUMMARY OF THE INVENTION
A smart circuit breaker containing a microprocessor within its electronic
trip unit is arranged as a main circuit breaker within a switchboard or
panelboard enclosure. A plurality of branch circuit breakers containing
electronic trip units without a microprocessor are electrically
interconnected with the microprocessor within the main circuit breaker.
Zone-Selective-Interlock and Load Selection functions are provided by
operation of the shunt trip and auxiliary switch accessories contained
within the branch circuit breakers.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front plan view of a switchboard or panelboard enclosure
containing a main circuit breaker and distributed branch circuit breakers
interconnected in accordance with the invention;
FIG. 2 is a top perspective view of the main circuit breaker used within
the switchboard or panelboard enclosure of FIG. 1;
FIG. 3 is a top perspective view in isometric projection, of one of the
branch circuit breakers used within the switchboard or panelboard
enclosure of FIG. 1;
FIG. 4 is a schematic representation of the electronic trip unit used
within the branch circuit breaker depicted in FIG. 3;
FIG. 5 is a schematic representation of the electronic trip unit used
within the main circuit breaker depicted in FIG. 2;
FIG. 6 is a diagrammatic representation of the main and branch circuit
breakers depicted within the switchboard or panelboard enclosure of FIG. 1
connected in a double-branch arrangement;
FIG. 7 is a flow chart representation of the control program used with the
main and branch circuit breakers within the switchboard or panelboard of
FIG. 1;
FIG. 8 is a flow chart representation of a Zone-Selective-Interlock program
used with the main and branch circuit breaker within the switchboard or
panelboard of FIG. 1 when the main circuit breaker is in the short-time
pick-up mode;
FIG. 9 is a flow chart representation of the Load Selection program and
Zone-Selective-Interlock program used with the main and branch circuit
breakers within the panelboard or switchboard of FIG. 1, when the main
circuit breaker is in the long-time pick-up mode; and
FIG. 10 is a flow chart representation of the Load Selection program used
with the main and branch circuit breakers within the panelboard or
switchboard of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A switchboard or panelboard 10 of the type consisting of an extended metal
enclosure 11 is shown in FIG. 1 and includes a plurality of closed
compartments 12 that are accessible by means of a compartment handle 25.
One of the compartments contains a main circuit breaker 13 similar to that
described in the aforementioned U.S. Pat. No. 4,991,042 and includes a
handle 14 extending from a handle escutcheon 14A and a keypad 15 along
with a display 16. The handle, keypad and display are accessible through
an inverted T-shaped slot 20 formed within the front surface of the
compartment. As described within the aforementioned U.S. patent
application Ser. No. 674,475 the main circuit breaker is connected to a
terminal board 17 by means of a cable 19. The main terminal board includes
a plurality of main terminals 18 that interconnect with corresponding
branch terminals 18' associated with similar branch terminal boards 17'.
The branch terminal boards each connect with one of the branch circuit
breakers 21A by means of a similar cable 19'. The branch circuit breakers
are similar to those described within U.S. Pat. No. 4,754,247 entitled "
Molded Case Circuit Breaker Accessory Enclosure". Each of the branch
circuit breakers has an operating handle 22 extending from the handle
escutcheon 22A along with the trip-test button 24 which are both
accessible through a slot 23 formed through a front surface of the
compartment. Similar branch circuit breakers 21B-21F are located within
the remaining closed compartments.
The main circuit breaker 13 is best seen by referring now to FIG. 2 wherein
the main circuit breaker contains a case 26 to which a circuit breaker
cover 27 is fixedly attached and which includes an accessory cover 28
attached to the circuit breaker cover. The keypad 15 and display 16
described within the aforementioned U.S. Pat. No. 4,991,042 are arranged
under a protective plastic plate 29 and can be accessed for inputting and
displaying the trip parameters by first removing the protective plate. As
described in the aforementioned U.S. patent application Ser. No. 674,475
the terminal board 17 is connected to the load end of the main circuit
breaker cover by means of the multi-conductor cable 19. Electrical
connection with the electronic trip unit contained within the main circuit
breaker cover is made by means of the terminals 18. For purposes to be
described below in greater detail, the terminals 18 are allocated to the
branch circuit breakers (21A-21F) by designating the terminal connectors
100 (A-F), 101 (A-F) and 102 (A-F) accordingly wherein the letters ("A-F")
designate the (A-F) branches of the protected power circuit and the
numerals (100-102) designate the Pick-Up (P.U.), Shunt Trip (S.T.) and
Auxiliary Switch (A.S.) connectors. The group of terminal connectors 100
(A-F) designated "P.U." are allocated for connection with the pick-up
indication terminals from electronic trip units within each of the
associated branch circuit breakers. The group of terminal connectors 101
(A-F) designated "S.T." are allocated for connection with corresponding
branch circuit breaker terminals connecting with the actuator-accessory
units 33 (FIG. 3) contained within the branch circuit breaker covers. The
group of terminal connectors 102 (A-F) designated "A.S." are allocated for
connection with corresponding branch circuit breaker terminals connecting
with the auxiliary switch units 40 (FIG. 3) contained within the branch
circuit breaker covers. Terminal connector 103 connects with systems
ground.
One of the branch circuit breakers 21A is depicted in FIG. 3 prior to final
assembly. The branch circuit breaker has a similar case 26, cover 27 and
accessory cover 28 as the main circuit breaker, described earlier and
common reference numerals for both the main circuit breaker and branch
circuit breaker components will be used where possible. An
actuator-accessory unit 33 of the type described within U.S. Pat. No.
4,894,631 is positioned within the accessory-actuator recess 33A and
interacts with the circuit breaker operating mechanism (not shown) by
means of the actuator latch 34. The actuator-accessory unit responds to
signals generated by the electronic trip unit 37 within the trip unit
recess 37A over wire conductor 35 to articulate the circuit breaker
operating mechanism and separate the circuit breaker contacts (not shown).
The actuator-accessory unit also responds to trip signals generated from a
remote location over the shunt-trip wire conductor 36 that passes under
the branch circuit breaker through a slot 67 and then upwards within a
wiring channel 43 formed within the case 26. The shunt-trip wire conductor
passes through the multi-conductor cable 19 to the branch terminal board
17' and is electrically connected to one of the terminal connectors
designated (101A) "S.T". The operation of the actuator-accessory unit 33
as a shunt-trip accessory is described within U.S. Pat. No. 4,858,056
entitled "Molded Case Circuit Breaker Actuator-Accessory Module". The
electric circuit for controlling the operation of the actuator-accessory
module as a shunt-trip accessory is found within U.S. Pat. No. 4,860,157
entitled "Molded Case Circuit Breaker Actuator-Accessory Module". An
auxiliary switch accessory 40 is inserted within an auxiliary switch
recess 40A also formed within the branch circuit breaker cover 27. The
auxiliary switch interacts with the branch circuit breaker operating
mechanism by means of an actuator lever 41 to provide a signal over the
auxiliary switch wire conductor 42 which passes through an opening (not
shown) in the bottom of the auxiliary switch recess 40A to the wiring
channel 43 and then out to the branch terminal board 17' via cable 19. The
auxiliary switch wire conductor 42 connects with another one of the
terminal connectors designated (102A) "A.S.". The electronic trip unit 37
in the circuit breaker cover 27 electrically connects with the branch
terminal board 17' by means of the pick-up indicator wire conductor 46
which exits through the bottom of the auxiliary switch recess 40A and the
wiring channel 43 out through the cable 19 and connects with the end of
the terminal designated (100A) "P.U.". The terminal connector 103
similarly connects with systems ground as described earlier. A rating plug
30 is inserted within the rating plug recess 30A formed in the accessory
cover 28 and electrically connects with the trip unit 37 by means of
sockets 38 formed on the bottom of the rating plug and upstanding pins 39
formed on the trip unit 37. The accessory cover 28 is securely fastened to
the branch circuit breaker cover 27 by means of machine screws 68,
thru-holes 69 and threaded openings 70 as indicated. Access to the
actuator-accessory unit 33 is made by means of the accessory door 31 and
access to the auxiliary switch 40 is made by means of the other accessory
door 32. The remaining branch circuit breakers 21B-21F also have similar
terminals 18 containing corresponding terminal connectors 100 (B-F)
"P.U.", 101 (B-F) "S.T." and 102 (B-F) "A.S." respectively.
The trip unit circuit 58 used within the trip unit 37 is depicted in FIG. 4
and includes an integrated circuit trip unit 49 similar to that described
within the aforementioned U.S. Pat. No. 4,589,052. The trip unit connects
with the multi-phase power conductors 55 and associated current
transformers 56 through a signal conditioning circuit 47. The signal
conditioning circuit includes a rectifier 50 wherein the current signals
are changed to a DC configuration and applied across the rating resistor
R.sub.b for providing circuit current data to the trip unit over wire
conductor 71. The signal conditioning circuit includes a power supply 51
that derives its operating power from the current transformers and which
inputs operating power to the trip unit over conductor 72. As fully
described within aforementioned U.S. Pat. No. 4,589,052, a trip actuator
circuit 48 controls the condition of the circuit breaker contacts 57 that
are serially connected within the multi-phase power conductors 55. A trip
output signal from the trip unit controls the driver circuit 54 which
connects with the trip coil 52 through an SCR 53 to separate the circuit
breaker contacts upon the occurrence of an overcurrent condition of
predetermined duration through the multi-phase power conductors. The pin
connectors (1-3) on the trip unit connect with an externally accessible
switch over conductor 73 to vary the instantaneous and short-time trip
parameters stored within the trip unit. Pin connector 4 connects with
terminal connection 100A (P.U.) on the branch terminal board 17' over
conductor 46 (FIG. 3) for providing information as to the occurrence of a
long-time or short-time overcurrent condition occurring on the multi-phase
power conductors in a manner to be discussed below in greater detail.
The trip unit circuit 59 depicted in FIG. 5 is used within the trip unit
contained within the main circuit breaker 13 shown earlier in FIG. 2 and
includes a microprocessor 60 that connects with a similar signal
conditioner circuit 47 and trip actuator circuit 48 to separate the
circuit breaker contacts 57 serially connected within the multi-phase
power conductors 55. The current data through the multi-phase power
conductors is transmitted to the microprocessor by means of the current
transformers 56, signal conditioner circuit 47 and the wire conductors 64
as indicated. As fully described within the aforementioned U.S. Pat. No.
4,991,042 the operating programs for the microprocessor are stored in the
ROM 62 and the trip parameter values are stored in the RAM 61 both of
which connect with the microprocessor I/O ports 24, 25 by means of the 12
BIT address and 8 BIT data buses 63, 64. I/O ports 1-6 connect with the
externally accessible keypad switches 15 (FIG. 2) to enter and display the
trip parameters stored within the RAM 61. I/O ports 7-12 connect with the
corresponding pick-up indicating terminal connectors 100 (A-F) "P.U." on
the branch terminal boards 17' connected with the branch circuit breakers
21 (A-F) shown in FIGS. 1 and 3. The I/O ports (13-18) connect with the
corresponding branch shunt trip terminal connectors 101 (A-F) "S.T." and
the I/O ports (19-24) connect with the corresponding branch auxiliary
switch terminal connectors 102 (A-F) "A.S" in a manner to be described
below in greater detail.
A double-branch circuit arrangement 66 for the main circuit breaker 13 and
branch circuit breakers (21A-21F) (FIG. 1) is depicted in FIG. 6. Branch
circuit breaker 21A protects branch circuit A which in turn connects in
series with branch circuits C, D as indicated. Branch circuit breaker 21B
protects branch circuit B which connects in series with branch circuits E
and F. The branch circuits (C-F) each include corresponding branch circuit
breakers (21C-21F).
The Zone-Selective-Interlock function (Z.S.I.) and Load Selection function
(L.S.) for the branch circuit breakers (21A-21F) can be seen by referring
now to FIGS. 2, 3, 5 and 6. The main terminal 17 of the main circuit
breaker 13 of FIGS. 1 and 2 is arranged such that each of the branch
terminal connectors 100 (A-F) "P.U.", 101 (A-F) "S.T.", and 102 (A-F)
"A.S." connects with a corresponding main terminal 18 on the main terminal
board 17. The Z.S.I. function is performed as follows. Upon occurrence of
an overcurrent condition within one of the branch circuit breakers 21C, as
shown for example, in FIG. 6, the appropriate signal of the pick-up
indication is transmitted from the associated branch terminal board 17' to
the main terminal board 17. The microprocessor can then delay operation of
the main circuit breaker and activate the actuator-accessory unit within
the branch circuit breaker 21C by outputting a shunt trip signal over the
appropriate I/O port (13-18) to articulate the operating mechanism and
separate the contacts within the branch circuit breaker 21C. The auxiliary
switch unit within the branch circuit breaker 21C then closes and outputs
an auxiliary switch signal indication to the microprocessor over the
appropriate I/O port (19-24) to indicate to the microprocessor that the
branch circuit breaker 21C has responded to interrupt the fault. The
Z.S.I. function accordingly deters the operation of the upstream branch
circuit breaker to allow the downstream branch circuit breaker closest to
the fault to interrupt the circuit current.
The L.S. function is performed by assigning the branch circuit breakers
21C, 21D, 21E and 21F a priority with respect to operation. Critical
equipment such as emergency lighting, computers and medical equipment are
prioritized and peripheral equipment such as air conditioners and
machinery are shut down before the critical equipment. When the total
current through the branch circuit breakers 21C and 21D exceeds the ampere
rating of the upstream branch circuit breaker 21A, a pick-up indication
signal is transmitted to the appropriate I/O port (7-12) on the
microprocessor 60. The microprocessor then determines whether the
downstream circuit breakers 21C, 21D are also experiencing an overcurrent
condition. If not, the nonessential equipment is interrupted by actuating
the associated actuator-accessory unit in the non-prioritized branch
circuit breaker 21C or 21D. The appropriate auxiliary switch signal is
transmitted by the branch circuit breaker to the appropriate I/O port
(19-24) to signify to the microprocessor that the selected branch circuit
breaker has responded.
The instructions to the microprocessor for performing the Z.S.I. functions
are depicted in the flow chart diagram 75 as shown in FIG. 7. Upon
start-up, the microprocessor is initialized (76) and inquiry is made as to
whether the main circuit breaker is in pick-up (77). If it is determined
that the main circuit breaker is in pick-up, an inquiry is made as to
whether the trip time delay in the main circuit breaker electronic trip
unit is started (78). If not, the trip time delay is begun (79). If the
trip time delay in the main circuit breaker is started, inquiry is made as
to whether the trip response of the main circuit breaker is inhibited (80)
and if not, whether the time delay is over (81). If the trip function
within the main circuit breaker is inhibited, inquiry is made as to
whether the pick-up mode is short-time (83). If the time delay is over,
the electronic trip unit within the main circuit breaker is initiated, the
main circuit breaker is tripped (82) and the loop is continued by again
determining whether the main circuit breaker is in pick-up. If the time
delay is not over, the control program continues along branch 84 or branch
85 depending upon the magnitude of the overcurrent condition in the main
circuit breaker.
The short-time delay operating program (84) is depicted in FIG. 8 and
determines whether the A branch breaker is in pick-up (86) and if so, a
shunt trip signal is inputted to the trip unit of the A branch breaker to
trip the A branch breaker (87) and inquiry is made as to whether the B
branch breaker is in pick-up (88). If it is determined that the A branch
breaker is not in pick-up, and the B branch is in pick-up then the shunt
trip signal is inputted to the trip unit within the B branch breaker (89).
If the B branch breaker is not in pick-up, the trip inhibit to the main
circuit breaker is cancelled (90).
The long-time operating program 85 is depicted in FIG. 9 and begins with an
inquiry as to whether the A branch breaker is in pick-up (91). If so, the
trip unit within the main circuit breaker is inhibited (92). If the A
branch breaker is not in pick-up an inquiry is made as to whether the B
branch breaker is in pick-up (93). If the B branch breaker is in pick-up,
the main breaker trip unit is inhibited (92) and the loop is continued. If
the B branch breaker is not in pick-up, the main circuit breaker trip unit
inhibit is cancelled (94) and an inquiry is made as to whether the
contacts in the A branch breaker are closed (95). If the contacts in the A
branch breaker are closed, a shunt-trip signal is inputted to the trip
unit within the A branch breaker (98). If the contacts in the A branch
breaker are not closed, inquiry is made as to whether the contacts in the
B branch breaker are closed (96). If the contacts in the B branch breaker
are closed, a shunt-trip signal is inputted to the trip unit within the B
branch breaker (97).
The branch Load Selection programs controlling the microprocessor 60 of
FIG. 5 for the main and branch circuit breakers depicted earlier in FIG. 6
are depicted in FIGS. 7 and 10 as follows. When it is determined that the
main breaker is not in pick-up (77) the branch load select flow diagram
(104) is initiated whereby an inquiry is made as to whether the A branch
circuit breaker is in pick-up (105) and if so, whether the C branch
circuit breaker is in pick-up (106). If the C branch circuit breaker is
not in pick-up, an inquiry is made as to whether the D branch circuit
breaker is in pick-up (107) and if not, a shunt trip signal is inputted to
the trip unit within the D branch circuit breaker (108). If the A branch
circuit breaker is in pick-up and either the C branch circuit breaker or
the D branch circuit breaker is in pick-up, then inquiry is made as to
whether the B branch circuit breaker is in pick-up. If the A branch
circuit breaker is not in pick-up, inquiry is made as to whether the B
branch circuit breaker is in pick-up (109) and if so, inquiry is made as
to whether the E branch circuit breaker is in pick-up (110). If the E
branch circuit breaker is not in pick-up, inquiry is made whether the F
branch circuit breaker is in pick-up (111) and if not, a shunt trip signal
is inputted to the trip actuator within the F branch circuit breaker
(112). If the E branch circuit breaker is in pick-up, or the F branch
circuit breaker is in pick-up, the loop is continued.
It has accordingly been shown that a "smart" circuit breaker employing a
microprocessor and related ROM and RAM memory can include internal
operating programs and external terminal connections with circuit
interrupters having an electronic trip unit and an electrically actuated
accessory-actuator unit. When a plurality of such electronic circuit
breakers are connected within a common enclosure, the associated terminal
connector boards are interconnected with the smart circuit breaker in a
"master-slave" relation whereby the smart circuit breaker controls the
tripping sequence of the branch circuit breakers for
Zone-Selective-Interlock and Load Selection functions.
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